THE DISCOVERY OF CANCER IN PLANTS
certain other diseases which are known
to be of parasitic origin.
Dr. Borrel, of the Pasteur Institute,
has found animal parasites (acarids)
buried in the cell masses of certain can
cers of the face, and he conceives that
possibly these parasites introduce an or
ganism or a poison much in the same
way as the mosquito introduces the ma
laria virus into the system. Still more
recently (1911-1912) Dr. Peyton Rouse
has announced* that a chicken sarcoma
(cancer) is inoculable in the absence of
cancer cells, and that the tumor material,
even when dried for six months, is still
infectious.
THE LATEST DISCOVERY
But perhaps the strongest support of
the parasitic theory of cancer has come
from what at first sight would seem to
be the most unlikely source, namely, the
Bureau of Plant Industry of the U. S.
Department of Agriculture. This, how
ever, is not so remarkable when we re
member that cancer is a disease result
ing from abnormal cell stimulation, and
that the cell is substantially the same in
both plants and animals.
Indeed it is to comparative pathology
that we must look for the most striking
results of our future investigation.
For some nine years past Dr. Erwin F.
Smith, the pathologist in charge of the
Laboratory of Plant Pathology of the
Department of Agriculture, and his as
sistants have been conducting a series of
investigations into the origin and his
tology of the crown gall.
The crown gall is a plant disease which
causes an annual loss to farmers of mil
lions of dollars and has become a serious
problem to the agriculturist on account
of the number of species of planL. liable
to its ravages. It is known to attack the
daisy, the almond, peach, and other stone
fruits, the apple, quince, raspberry, black
berry, the rose, the grape, red clover,
alfalfa, cotton, hops, sugar-beets, and va
rious shrubs, hot-house plants, and shade
trees. Up to the time that Dr. Smith
undertook his investigations its cause and
character were entirely unknown.
* Journal American Medical Association;
American Association for Cancer Research;
Journal Experimental Medicine.
A NEW BACILLUS FOUND
He has proved the parasitic nature of
this disease (Bulletin 213), and now
states (Bulletin 255) that it is nothing
more or less than a plant cancer, since it
is due to parasitic stimulation going on
within the cells and leading to abnormal
proliferations essentially like those pres
ent in cancer of men and animals.
While Dr. Smith has surrounded his
conclusions with all those qualifications
so dear to the modesty of the scientist,
there is no doubt that he has made a dis
covery of the first magnitude in pa
thology, and has indicated a line of re
search which investigators of human
cancer will be unable to ignore.
In 1904 the Department of Agriculture
received a number of margurites, or
Paris daisy plants, which were infected
with gall-like growths on the stems and
leaves. They were sent in to the De
partment by one of the large commercial
growers in New Jersey, accompanied by
the statement that the galls appeared,
without apparent cause, both on plants
grown in the open in summer and under
glass in winter.
HOW THE DAISY HELPED
The first result obtained from the in
vestigations undertaken by Dr. Smith
was the establishment of the fact that
these growths were not due to insect in
juries. The next step was to discover
whether the galls were due to infection
by fungous growths, and this was de
cided in the negative after very conclu
sive experiments.
The possibility of
these growths being due to bacteria next
presented itself and was investigated,
but for some time the results obtained
from the experiments were so inconclu
sive that the bacterial hypothesis was
temporarily abandoned. Every effort
was then made to produce the galls by
mechanical injuries practised upon the
plants in every stage of growth, but ex
periments in this direction were fruitless.
More than two years of careful in
vestigation had been consumed before
Dr. Smith and his assistants were able,
by bacteriological culture-methods, to iso
late any organism which would reproduce
the disease when plants were inoculated